<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
    <style>
    *{margin: 0;padding: 0}
    div{
        width: 300px;
        height: 300px;
        background: pink;
        padding: 20px;
    }
    /* 元素内容的启示位置是基于它自身width，height的起始位置 */
    </style>
</head>
<body>
    <div>
        hello world
    </div>
</body>
</html>